1. Field of the Invention
The present invention relates to a rubber waterproof plug and a manufacturing method of the same rubber waterproof plug, and more specifically to a rubber waterproof plug for a connector, which is clamped to a wire by a terminal and then inserted into a terminal accommodation chamber of tile connector to waterproof a gap between the wire and an inner wall of the terminal accommodation chamber.
2. Description of Related Art
An example of the rubber waterproof plug for a connector is disclosed in Japanese Published Unexamined (Kokai) Utility Model Application No. 62-163879, which is formed of a soft synthetic rubber integrally. The rubber waterproof plug is composed of a clamp connection portion clamped to a wire end by a clamp portion of a terminal and a seal portion brought into tight contact with an inner wall of a terminal accommodation chamber of the connector housing. In assembly, a wire is passed through a central hole of the waterproof plug in an axial direction thereof under airtight condition, and further the waterproof plug is fixed to the wire by clamping the clamp connection portion of the waterproof plug to the outer circumferential surface of the wire by use of the clamp portion of the terminal. The seal portion is formed with a plurality of annular lip portions projecting radially outward from the outer circumference of the seal portion. Therefore, when the waterproof plug is inserted into the terminal accommodation chamber these annular lip portions are brought into tight contact with the inner wall of the terminal accommodation chamber, so that it is possible to seal a gap between the outer circumference of the wire and the inner wall of the terminal accommodation chamber of the connector housing.
When the rubber waterproof plug is inserted into the terminal accommodation chamber, the rubber waterproof plug connected to the terminal is inserted from a rear opening of the terminal accommodation chamber until the terminal is engaged with a flexible engage arm formed in the inner wall of the terminal accommodation chamber. Under these conditions, since the terminal can be fixed in the terminal accommodation chamber in position, the waterproof plug can be also accommodated in the terminal accommodation chamber. In addition, under these conditions, in the rubber waterproof plug inserted into the terminal accommodation chamber together with the terminal from the rear opening of the connector housing, since the annular lip portions are brought into tight contact with the inner wall of the terminal accommodation chamber, and further since the wire is also brought into tight contact with the inner wall of the waterproof plug, it is possible to securely waterproof an inner gap between the outer circumference of the wire and the inner circumference of the waterproof plug and an outer gap between the outer circumference of the waterproof plug and the inner wall of the terminal accommodation chamber.
In the conventional rubber waterproof plug, however, when the rubber waterproof plug is inserted deep into the terminal accommodation chamber of the connector housing excessively together with the terminal, a rear end of the waterproof plug is inserted deep into the terminal accommodation chamber from the rear opening thereof, so that a recessed portion is inevitably produced at the rear opening of the terminal accommodation chamber.
Further, when the terminal clamp portion is not clamped to the clamp connection portion of the waterproof plug accurately at a predetermined position, since the position of the waterproof plug can vary along the axial direction of the terminal accommodation chamber, the rear end portion of the waterproof plug is sometimes inserted excessively deep into the terminal accommodation chamber, so that a recessed portion is produced in the same way at the rear opening portion of the terminal accommodation chamber. Once this recessed portion is produced, since water tends to stay at this recessed portion, there exists such a problem in that the water staying at the recess portion enters a gap between the outer circumference of the waterproof plug and the inner wall of the terminal accommodation chamber, in particular when the connector housing is vibrated or heated.
To overcome this problem, it is possible to eliminate the recessed portion by inserting the waterproof plug to such a position that the rear end of the waterproof plug is flush with the rear end surface of the opening of the connector housing. In this case, when the large diameter annular lip portion of the seal portion is located at the rear opening end of the connector housing, the recessed portion may not be produced and thereby no water stays thereat. However, when the small diameter annular lip portion of the seal portion is located at the rear opening end of the connector housing, since a recessed portion is inevitably produced, water stays at this recessed portion.
To overcome this problem, it is possible to consider that the waterproof plug must be inserted into the terminal accommodation chamber in such a way that the large diameter annular lip portion is always located at the rear opening end surface of the connector housing. However, since the waterproof plug is formed of a soft rubber and therefore easily slipped or dislocated when or after attached, it is very difficult to locate the large diameter annular lip portion of the waterproof plug accurately always at the rear opening end surface of the connector housing.